ICD-10 Code C00.1 – Malignant neoplasm of external lower lip (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C00.1 – Malignant neoplasm of external lower lip
What it is
C00.1 identifies a malignant tumor arising on the external lower lip. Use it for primary lip cancer documented on the outer lip surface, not for benign lesions or unspecified oral sites.
Clinical signs
Common findings include a persistent ulcer, indurated or crusted lesion, bleeding, or a nonhealing lip mass. Clinical features vary; refer to documentation.
When to use this code
Use C00.1 when the provider documents cancer of the external lower lip, including biopsy-confirmed malignancy or a clearly stated clinical diagnosis. Apply it only when the site is specifically the outer lower lip and not another oral cavity location. Check documentation if laterality or extent is unclear.
Do not use for
Do not use this code for benign lip lesions, premalignant changes, or malignant disease of the inner lip or oral cavity. If the record only says “lip cancer” without site detail, check documentation.
Coding tip
Confirm the note specifies “external lower lip” before assigning C00.1.